qabstractscrollarea.cpp

奇趣公司比较新的qt/emd版本

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#include "qabstractscrollarea.h"

#ifndef QT_NO_SCROLLAREA

#include "qscrollbar.h"
#include "qapplication.h"
#include "qstyle.h"
#include "qstyleoption.h"
#include "qevent.h"
#include "qdebug.h"
#include "qboxlayout.h"
#include "qpainter.h"

#include "qabstractscrollarea_p.h"
#include <qwidget.h>

#ifdef Q_WS_MAC
#include <qmacstyle_mac.h>
#include <private/qt_mac_p.h>
#endif

/*!
    \class QAbstractScrollArea
    \brief The QAbstractScrollArea widget provides a scrolling area with
    on-demand scroll bars.

    \ingroup abstractwidgets

    QAbstractScrollArea is a low-level abstraction of a scrolling
    area. The area provides a central widget called the viewport, in
    which the contents of the area is to be scrolled (i.e, the
    visible parts of the contents are rendered in the viewport). 

    Next to the viewport is a vertical scroll bar, and below is a
    horizontal scroll bar. When all of the area contents fits in the
    viewport, each scroll bar can be either visible or hidden
    depending on the scroll bar's Qt::ScrollBarPolicy. When a scroll
    bar is hidden, the viewport expands in order to cover all
    available space. When a scroll bar becomes visible again, the
    viewport shrinks in order to make room for the scroll bar.

    It is possible to reserve a margin area around the viewport, see
    setViewportMargins(). The feature is mostly used to place a
    QHeaderView widget above or beside the scrolling area. Subclasses
    of QAbstractScrollArea should implement margins.

    When inheriting QAbstractScrollArea, you need to do the
    following:

    \list
        \o Control the scroll bars by setting their
           range, value, page step, and tracking their
           movements.
        \o Draw the contents of the area in the viewport according
           to the values of the scroll bars.
        \o Handle events received by the viewport in
           viewportEvent() - notably resize events.
    \endlist

    With a scroll bar policy of Qt::ScrollBarAsNeeded (the default),
    QAbstractScrollArea shows scroll bars when they provide a non-zero
    scrolling range, and hides them otherwise.

    The scroll bars and viewport should be updated whenever the viewport
    receives a resize event or the size of the contents changes.
    The viewport also needs to be updated when the scroll bars
    values change. The initial values of the scroll bars are often
    set when the area receives new contents. 

    We give a simple example, in which we have implemented a scroll area
    that can scroll any QWidget. We make the widget a child of the
    viewport; this way, we do not have to calculate which part of
    the widget to draw but can simply move the widget with
    QWidget::move(). When the area contents or the viewport size
    changes, we do the following: 

    \quotefromfile snippets/myscrollarea.cpp
    \skipto areaSize
    \printto /^\}/

    When the scroll bars change value, we need to update the widget
    position, i.e., find the part of the widget that is to be drawn in
    the viewport:

    \quotefromfile snippets/myscrollarea.cpp
    \skipto hvalue
    \printto /^\}/

    In order to track scroll bar movements, reimplement the virtual
    function scrollContentsBy(). In order to fine-tune scrolling
    behavior, connect to a scroll bar's
    QAbstractSlider::actionTriggered() signal and adjust the \l
    QAbstractSlider::sliderPosition as you wish.

    For convenience, QAbstractScrollArea makes all viewport events
    available in the virtual viewportEvent() handler. QWidget's
    specialized handlers are remapped to viewport events in the cases
    where this makes sense. The remapped specialized handlers are:
    paintEvent(), mousePressEvent(), mouseReleaseEvent(),
    mouseDoubleClickEvent(), mouseMoveEvent(), wheelEvent(),
    dragEnterEvent(), dragMoveEvent(), dragLeaveEvent(), dropEvent(),
    contextMenuEvent(),  and resizeEvent().

    QScrollArea, which inherits QAbstractScrollArea, provides smooth
    scrolling for any QWidget (i.e., the widget is scrolled pixel by
    pixel). You only need to subclass QAbstractScrollArea if you need
    more specialized behavior. This is, for instance, true if the
    entire contents of the area is not suitable for being drawn on a
    QWidget or if you do not want smooth scrolling.

    \sa QScrollArea
*/

QAbstractScrollAreaPrivate::QAbstractScrollAreaPrivate()
    :hbar(0), vbar(0), vbarpolicy(Qt::ScrollBarAsNeeded), hbarpolicy(Qt::ScrollBarAsNeeded),
     viewport(0), cornerWidget(0), left(0), top(0), right(0), bottom(0),
     xoffset(0), yoffset(0), viewportFilter(0)
{
}

QAbstractScrollAreaScrollBarContainer::QAbstractScrollAreaScrollBarContainer(Qt::Orientation orientation, QWidget *parent)
    :QWidget(parent), scrollBar(new QScrollBar(orientation, this)),
     layout(new QBoxLayout(orientation == Qt::Horizontal ? QBoxLayout::LeftToRight : QBoxLayout::TopToBottom)),
     orientation(orientation)
{
    setLayout(layout);
    layout->setMargin(0);
    layout->setSpacing(0);
    layout->addWidget(scrollBar);
}

/*! \internal
    Adds a widget to the scroll bar container.
*/
void QAbstractScrollAreaScrollBarContainer::addWidget(QWidget *widget, LogicalPosition position)
{
    QSizePolicy policy = widget->sizePolicy();
    if (orientation == Qt::Vertical)
        policy.setHorizontalPolicy(QSizePolicy::Ignored);
    else
        policy.setVerticalPolicy(QSizePolicy::Ignored);
    widget->setSizePolicy(policy);
    widget->setParent(this);

    const int insertIndex = (position & LogicalLeft) ? 0 : scrollBarLayoutIndex() + 1;
    layout->insertWidget(insertIndex, widget);
}

/*! \internal
    Retuns a list of scroll bar widgets for the given position. The scroll bar
    itself is not returned.
*/
QWidgetList QAbstractScrollAreaScrollBarContainer::widgets(LogicalPosition position)
{
    QWidgetList list;
    const int scrollBarIndex = scrollBarLayoutIndex();
    if (position == LogicalLeft) {
        for (int i = 0; i < scrollBarIndex; ++i)
            list.append(layout->itemAt(i)->widget());
    } else if (position == LogicalRight) {
        const int layoutItemCount = layout->count();
        for (int i = scrollBarIndex + 1; i < layoutItemCount; ++i)
            list.append(layout->itemAt(i)->widget());
    }
    return list;
}

/*! \internal
    Returns the layout index for the scroll bar. This needs to be
    recalculated by a linear search for each use, since items in
    the layout can be removed at any time (i.e. when a widget is
    deleted or re-parented).
*/
int QAbstractScrollAreaScrollBarContainer::scrollBarLayoutIndex() const
{
    const int layoutItemCount = layout->count();
    for (int i = 0; i < layoutItemCount; ++i) {
        if (qobject_cast<QScrollBar *>(layout->itemAt(i)->widget()))
            return i;
    }
    return -1;
}

/*! \internal
*/
void QAbstractScrollAreaPrivate::replaceScrollBar(QScrollBar *scrollBar,
                                                  Qt::Orientation orientation)
{
    Q_Q(QAbstractScrollArea);

    QAbstractScrollAreaScrollBarContainer *container = scrollBarContainers[orientation];
    bool horizontal = (orientation == Qt::Horizontal);
    QScrollBar *oldBar = horizontal ? hbar : vbar;
    if (horizontal)
        hbar = scrollBar;
    else
        vbar = scrollBar;
    scrollBar->setParent(container);
    container->scrollBar = scrollBar;
    container->layout->removeWidget(oldBar);
    container->layout->insertWidget(0, scrollBar);
    scrollBar->setVisible(oldBar->isVisibleTo(oldBar->window()));
    scrollBar->setInvertedAppearance(oldBar->invertedAppearance());
    scrollBar->setInvertedControls(oldBar->invertedControls());
    scrollBar->setRange(oldBar->minimum(), oldBar->maximum());
    scrollBar->setOrientation(oldBar->orientation());
    scrollBar->setPageStep(oldBar->pageStep());
    scrollBar->setSingleStep(oldBar->singleStep());
    scrollBar->setSliderDown(oldBar->isSliderDown());
    scrollBar->setSliderPosition(oldBar->sliderPosition());
    scrollBar->setTracking(oldBar->hasTracking());
    scrollBar->setValue(oldBar->value());
    delete oldBar;

    QObject::connect(scrollBar, SIGNAL(valueChanged(int)),
                     q, horizontal ? SLOT(_q_hslide(int)) : SLOT(_q_vslide(int)));
    QObject::connect(scrollBar, SIGNAL(rangeChanged(int,int)),
                     q, SLOT(_q_showOrHideScrollBars()), Qt::QueuedConnection);
}

void QAbstractScrollAreaPrivate::init()
{
    Q_Q(QAbstractScrollArea);
    scrollBarContainers[Qt::Horizontal] = new QAbstractScrollAreaScrollBarContainer(Qt::Horizontal, q);
    scrollBarContainers[Qt::Horizontal]->setObjectName(QLatin1String("qt_scrollarea_hcontainer"));
    hbar = scrollBarContainers[Qt::Horizontal]->scrollBar;
    hbar->setRange(0,0);
    scrollBarContainers[Qt::Horizontal]->setVisible(false);
    QObject::connect(hbar, SIGNAL(valueChanged(int)), q, SLOT(_q_hslide(int)));
    QObject::connect(hbar, SIGNAL(rangeChanged(int,int)), q, SLOT(_q_showOrHideScrollBars()), Qt::QueuedConnection);
    scrollBarContainers[Qt::Vertical] = new QAbstractScrollAreaScrollBarContainer(Qt::Vertical, q);
    scrollBarContainers[Qt::Vertical]->setObjectName(QLatin1String("qt_scrollarea_vcontainer"));
    vbar = scrollBarContainers[Qt::Vertical]->scrollBar;
    vbar->setRange(0,0);
    scrollBarContainers[Qt::Vertical]->setVisible(false);
    QObject::connect(vbar, SIGNAL(valueChanged(int)), q, SLOT(_q_vslide(int)));
    QObject::connect(vbar, SIGNAL(rangeChanged(int,int)), q, SLOT(_q_showOrHideScrollBars()), Qt::QueuedConnection);
    viewportFilter = new QAbstractScrollAreaFilter(this);
    viewport = new QWidget(q);
    viewport->setObjectName(QLatin1String("qt_scrollarea_viewport"));
    viewport->setBackgroundRole(QPalette::Base);
    viewport->setAutoFillBackground(true);
    viewport->installEventFilter(viewportFilter);
    viewport->setFocusProxy(q);
    q->setFocusPolicy(Qt::WheelFocus);
    q->setFrameStyle(QFrame::StyledPanel | QFrame::Sunken);
    q->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    layoutChildren();
}

void QAbstractScrollAreaPrivate::layoutChildren()
{
    Q_Q(QAbstractScrollArea);
    bool needh = (hbarpolicy == Qt::ScrollBarAlwaysOn
                  || (hbarpolicy == Qt::ScrollBarAsNeeded && hbar->minimum() < hbar->maximum()));

    bool needv = (vbarpolicy == Qt::ScrollBarAlwaysOn
                  || (vbarpolicy == Qt::ScrollBarAsNeeded && vbar->minimum() < vbar->maximum()));

    const int hsbExt = hbar->sizeHint().height();
    const int vsbExt = vbar->sizeHint().width();
    const QPoint extPoint(vsbExt, hsbExt);
    const QSize extSize(vsbExt, hsbExt);

    const QRect widgetRect = q->rect();
    QStyleOption opt(0);
    opt.init(q);

    const bool hasCornerWidget = (cornerWidget != 0);

// If the scroll bars are at the very right and bottom of the window we
// move their positions to be aligned with the size grip.
#ifdef Q_WS_MAC
    QWidget * const window = q->window();
    // Check if a native sizegrip is present.
    bool hasMacReverseSizeGrip = false;
    bool hasMacSizeGrip = false;
    HIViewRef nativeSizeGrip;
    HIViewFindByID(HIViewGetRoot(HIViewGetWindow(HIViewRef(q->winId()))), kHIViewWindowGrowBoxID, &nativeSizeGrip);
    if (nativeSizeGrip) {
        // Look for a native size grip at the visual window bottom right and at the
        // absolute window bottom right. In reverse mode, the native size grip does not
        // swich side, so we need to check if it is on the "wrong side".
        const QPoint scrollAreaBottomRight = q->mapTo(window, widgetRect.bottomRight() - QPoint(frameWidth, frameWidth));
        const QPoint windowBottomRight = window->rect().bottomRight();
        const QPoint visualWindowBottomRight = QStyle::visualPos(opt.direction, opt.rect, windowBottomRight);
        const QPoint offset = windowBottomRight - scrollAreaBottomRight;
        const QPoint visualOffset = visualWindowBottomRight - scrollAreaBottomRight;
        hasMacSizeGrip = (visualOffset.manhattanLength() < vsbExt);
        hasMacReverseSizeGrip = (hasMacSizeGrip == false && (offset.manhattanLength() < hsbExt));
    }

    // Use small scroll bars for tool windows, to match the native size grip.
    const QMacStyle::WidgetSizePolicy hpolicy = QMacStyle::widgetSizePolicy(hbar);
    const QMacStyle::WidgetSizePolicy vpolicy = QMacStyle::widgetSizePolicy(vbar);
    const Qt::WindowType windowType = window->windowType();
    if (windowType == Qt::Tool) {
        if (hpolicy != QMacStyle::SizeSmall)
            QMacStyle::setWidgetSizePolicy(hbar, QMacStyle::SizeSmall);
        if (vpolicy != QMacStyle::SizeSmall)
            QMacStyle::setWidgetSizePolicy(vbar, QMacStyle::SizeSmall);
    } else {
        if (hpolicy != QMacStyle::SizeDefault)
            QMacStyle::setWidgetSizePolicy(hbar, QMacStyle::SizeDefault);
        if (vpolicy != QMacStyle::SizeDefault)
            QMacStyle::setWidgetSizePolicy(vbar, QMacStyle::SizeDefault);
    }
#endif
    QPoint cornerOffset(needv ? vsbExt : 0, needh ? hsbExt : 0);
    QRect controlsRect;
    QRect viewportRect;

    // In FrameOnlyAroundContents mode the frame is drawn between the controls and
    // the viewport, else the frame rect is equal to the widget rect.
    if (q->style()->styleHint(QStyle::SH_ScrollView_FrameOnlyAroundContents, &opt, q)) {
        controlsRect = widgetRect;
        const int extra = q->style()->pixelMetric(QStyle::PM_DefaultFrameWidth) * 2;
        const QPoint cornerExtra(needv ? extra : 0, needh ? extra : 0);
        QRect frameRect = widgetRect;
        frameRect.adjust(0, 0, -cornerOffset.x() - cornerExtra.x(), -cornerOffset.y() - cornerExtra.y());
        q->setFrameRect(frameRect);
        viewportRect = q->contentsRect();
    } else {
        q->setFrameRect(QStyle::visualRect(opt.direction, opt.rect, widgetRect));
        controlsRect = q->contentsRect();
        viewportRect = QRect(controlsRect.topLeft(), controlsRect.bottomRight() - cornerOffset);
    }

    // If we have a corner widget and are only showing one scroll bar, we need to move it
    // to make room for the corner widget.
    if (hasCornerWidget && (needv || needh))
        cornerOffset =  extPoint;

#ifdef Q_WS_MAC
    // Also move the scroll bars if they are covered by the native Mac size grip.
    if (hasMacSizeGrip)
        cornerOffset =  extPoint;
#endif

    // The corner point is where the scroll bar rects, the corner widget rect and the
    // viewport rect meets.
    const QPoint cornerPoint(controlsRect.bottomRight() + QPoint(1, 1) - cornerOffset);

    // Some styles paints the corner if both scorllbars are showing and there is
    // no corner widget. Also, on the Mac we paint if there is a native
    // (transparent) sizegrip in the area where a corner widget would be.
    if (needv && needh && hasCornerWidget == false
#ifdef Q_WS_MAC
        || ((needv || needh) && hasMacSizeGrip)
#endif
    ) {
        cornerPaintingRect = QStyle::visualRect(opt.direction, opt.rect, QRect(cornerPoint, extSize));
    } else {
        cornerPaintingRect = QRect();
    }

#ifdef Q_WS_MAC
    if (hasMacReverseSizeGrip)
        reverseCornerPaintingRect = QRect(controlsRect.bottomRight() + QPoint(1, 1) - extPoint, extSize);
    else
        reverseCornerPaintingRect = QRect();
#endif

    if (needh) {
        QRect horizontalScrollBarRect(QPoint(controlsRect.left(), cornerPoint.y()), QPoint(cornerPoint.x() - 1, controlsRect.bottom()));
#ifdef Q_WS_MAC
        if (hasMacReverseSizeGrip)
            horizontalScrollBarRect.adjust(vsbExt, 0, 0, 0);
#endif
        scrollBarContainers[Qt::Horizontal]->setGeometry(QStyle::visualRect(opt.direction, opt.rect, horizontalScrollBarRect));
        scrollBarContainers[Qt::Horizontal]->raise();
    }

    if (needv) {
        const QRect verticalScrollBarRect  (QPoint(cornerPoint.x(), controlsRect.top()),  QPoint(controlsRect.right(), cornerPoint.y() - 1));
        scrollBarContainers[Qt::Vertical]->setGeometry(QStyle::visualRect(opt.direction, opt.rect, verticalScrollBarRect));
        scrollBarContainers[Qt::Vertical]->raise();
    }

    if (cornerWidget) {
        const QRect cornerWidgetRect(cornerPoint, controlsRect.bottomRight());
        cornerWidget->setGeometry(QStyle::visualRect(opt.direction, opt.rect, cornerWidgetRect));
    }